Vapor-permeable, substantially water-impermeable multilayer article

ABSTRACT

This disclosure relates to an article (e.g., a vapor-permeable, substantially water-impermeable multilayer article) that includes a nonwoven substrate and a film supported by the nonwoven substrate. The film includes a polyolefin, a nanoclay, and a pore-forming filler.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/523,028 filed on Jun. 14, 2012, and which claims priority toU.S. Provisional Patent Application No. 61/498,328 filed on Jun. 17,2011, and claims the benefit of the its earlier filing date under 35U.S.C. 119(e); each of U.S. patent application Ser. No. 13/523,028 andU.S. Provisional Patent Application No. 61/498,328 are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

This disclosure relates to vapor-permeable, substantiallywater-impermeable multilayer articles, as well as related products andmethods.

BACKGROUND

Polyolefin films that are rendered permeable to water vapor by using afiller and a stretching process are known. Such films are also known asbreathable, i.e., having vapor permeability while maintaining aresistance to water. They can permit the passage of moisture vapor andair, while substantially preventing the passage of water.

SUMMARY

This disclosure is based on the findings that including a nanoclay(e.g., montmorillonite nanoclay) in a film containing a pore-formingfiller (e.g., calcium carbonate) can provide an unexpected improvementin the flame retardancy of the film. Such a film can be combined with anonwoven substrate to form a multilayer article with improved flameretardancy, which is suitable for use as a construction material (e.g.,a housewrap or a roofwrap).

In one aspect, this disclosure features an article that includes a filmcontaining a polyolefin, a nanoclay, and a pore-forming filler.

In another aspect, this disclosure features an article that includes anonwoven substrate and a film supported by the nonwoven substrate,wherein the film includes a polyolefin, a nanoclay, and a pore-formingfiller.

In another aspect, this disclosure features an article that includes anonwoven substrate and a film supported by the nonwoven substrate,wherein the film has a maximum heat release time measured in a conecalorimetry test longer than that of a film having the same compositionexcept that it does not include both a nanoclay and a pore-formingfiller.

In another aspect, this disclosure features a construction material thatincludes at least one of the articles described above.

In still another aspect, this disclosure features a method of making anarticle. The method includes forming a laminate containing a nonwovensubstrate and a film supported by the nonwoven substrate; and stretchingthe laminate to form the article. The film includes a polyolefin, ananoclay, and a pore-forming filler.

Embodiments can include one or more of the following optional features.

The nanoclay can include montmorillonite clay.

The nanoclay can include particles having an average aspect ratio offrom about 200 to about 500.

The film can include from about 0.1% by weight to about 20% by weight(e.g., about 2% by weight) of the nanoclay.

The polyolefin can include a polyethylene, a polypropylene, or acopolymer thereof. For example, the polyolefin can include apolyethylene selected from the group consisting of low-densitypolyethylene, linear low-density polyethylene, and high densitypolyethylene. In some embodiments, the film can further include afunctionalized polyolefin.

The pore-forming filler can include calcium carbonate. In someembodiments, the film can include from about 30% by weight to about 70%by weight (e.g., about 50% by weight) of the calcium carbonate.

The film can further include an elastomer. For example, the elastomercan be a thermoplastic olefin elastomer (e.g., a propylene-ethylenecopolymer). In some embodiments, the film can include from about 5% byweight to about 30% by weight of the elastomer.

The nonwoven substrate can include randomly disposed polymeric fibers,at least some of which are bonded to one another.

The article can have a moisture vapor transmission rate of at leastabout 35 g/m²/day when measured at 23° C. and 50% relative humidity (RH%).

When the article has a unit weight of 1.25 ounces per square yard (osy),the article can have a tensile strength of at least about 40 pounds inthe machine direction as measured according to ASTM D5034 and/or atleast about 35 pounds in the cross-machine direction as measuredaccording to ASTM D5034.

The article can have a hydrostatic head of at least about 55 cm.

The film can have a maximum heat release time measured in a conecalorimetry test longer than that of a film having the same compositionexcept for the nanoclay, the pore-forming filler, or both.

The article can be embossed.

The construction material can be a housewrap or a roofwrap.

Forming the laminate can include extruding the film onto the nonwovensubstrate.

The laminate can be stretched at an elevated temperature (e.g., at leastabout 30° C.).

The laminate can be stretched in the machine direction or in thecross-machine direction.

The laminate can be stretched by a method selected from the groupconsisting of ring rolling, tentering, embossing, creping, andbutton-breaking.

The method can further include embossing the laminate prior to or afterstretching the laminate.

The method can further include bonding randomly disposed polymericfibers to produce the nonwoven substrate prior to forming the laminate.

Embodiments can provide one or more of the following advantages.

In some embodiments, including a nanoclay (e.g., montmorillonitenanoclay) in a film containing a pore-forming filler (e.g., calciumcarbonate) can achieve a synergistic effect in the flame retardancy ofthe film as demonstrated by an unexpected increase in its maximum heatrelease time measured in a cone calorimetry test.

In some embodiments, one advantage of using an elastomer in a breathablefilm is that a multilayer article containing such a film can have bothimproved tensile strength and improved elongation.

In some embodiments, when the surface of the breathable film contains apolymer having a chemical structure similar to or the same as thechemical structure of a polymer in the surface of the nonwovensubstrate, the multilayer article thus formed can have improved adhesionbetween the breathable film and the nonwoven substrate.

In some embodiments, stretching the laminate described above at anelevated temperature (e.g., at least about 30° C.) can unexpectedlyimprove the moisture vapor transmission rate of the multilayer articlethus formed while still maintaining an appropriate hydrostatic head ofthe multilayer article.

Other features and advantages will be apparent from the description,drawings, and claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a vapor-permeable, substantiallywater-impermeable multilayer article.

FIG. 2 is a scheme illustrating an exemplary extruding process.

FIG. 3 is a scheme illustrating an exemplary ring-rolling apparatus.

FIG. 4 is a plot illustrating the results of various multilayer articlesin a cone calorimetry test.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

This disclosure relates to, for example, an article (e.g., avapor-permeable, substantially water-impermeable multilayer article)containing a film (e.g., a breathable film) supported by a nonwovensubstrate. The film can include a polyolefin, a nanoclay, a pore formingfiller, and optionally an elastomer. The nonwoven substrate can beformed from polymeric fibers.

FIG. 1 is a cross-sectional view of a vapor-permeable, substantiallywater-impermeable multilayer article 10 containing a breathable film 12supported by a nonwoven substrate 14.

A nanoclay can include a clay from the smectite family. Smectitenanoclays have a unique morphology, featuring one dimension in thenanometer range. An example of a smectite nanoclay is montmorillonitenanoclay. The montmorillonite nanoclay particle is often called aplatelet, which has a sheet-like structure where the dimensions in twodirections far exceed the particle's thickness. Other suitable nanoclaysare disclosed, for example, in U.S. Pat. No. 6,414,070, and PCTApplication Publication Nos. WO 00/66657 and WO 00/68312.Montmorillonite nanoclays are commercially available from Nanocor, Inc.

In some embodiments, the nanoclay used in the film 12 can beintercalated with an intercalant. An intercalate is a clay-chemicalcomplex in which the space between parallel layers of the clay plateletshas increased, e.g., by surface modification using an intercalant. Anintercalant is a chemical capable of entering the space between clayplatelets. Montmorillonite nanoclays containing an intercalant are alsocommercially available. An example of such a nanoclay is NANOMER I44Pavailable from Nanocor, Inc.

In some embodiments, the nanoclay particles (i.e., nanoclay platelets)can have an average length or width of at least about 0.1 μm (e.g., atleast about 0.5 μm) and/or at most about 1.5 μm (e.g., at most about 1.0μm), while having an average thickness of at least about 0.5 nm (e.g.,at least about 1 nm) and/or at most about 2 nm (e.g., at most about 1.5nm). Thus, the nanoclay particle can have a large average aspect ratio(e.g., a ratio between length and thickness or a ratio between width andthickness). For example, the average aspect ratio of a nanoclay particlecan be at least about 200 (e.g., at least about 250) and/or at mostabout 500 (e.g., at most about 400 or at most about 300).

The film 12 can include the nanoclay in an amount that can providesufficient flame retardancy. For example, the film 12 can include fromat least about 0.1% (e.g., at least about 0.5% or at least about 1%) toat most about 20% (e.g., at most about 15%, at most about 10%, at mostabout 5%, at most about 4% or at most about 3%) by weight of thenanoclay. In one example, the film 12 can include about 2% by weight ofthe nanoclay.

Without wishing to be bound by theory, it is believed that including ananoclay (e.g., montmorillonite nanoclay) in a film containing apore-forming filler (e.g., calcium carbonate) can achieve a synergisticeffect in the flame retardancy of the film. The flame retardancy of afilm can be characterized by the maximum heat release time measured in acone calorimetry test according to ASTM E1354. As used herein, the term“maximum heat release time” refers to the time required for aheat-release curve (i.e., a curve of the heat-release rate of a filmover the entire period of time of the cone calorimetry test) to attainits maximum value. In general, the longer the maximum heat-release time,the better the flame retardancy. As an example, when a polypropylenefilm includes either the nanoclay or the pore-forming filler (but notboth), the film can have a maximum heat-release time measured in a conecalorimetry test shorter (e.g., by about 5-15%) than that of apolypropylene film without any additive (i.e., without the nanoclay orthe pore-forming filler). Unexpectedly, when a propylene film includesboth the nanoclay and the pore-forming filler, the film can have amaximum heat-release time measured in the cone calorimetry test longer(e.g., by at least about 5%) than that of a propylene film without anyadditive, which in turn is longer than that of a propylene film havingeither the nanoclay or the pore-forming filler. In other words, apropylene film including both the nanoclay and the pore-forming fillerpossesses significantly better flame retardancy than that of apolypropylene without any additive or with only of the nanoclay or thepore-forming filler. In addition, a multilayer article including theformer film also possesses significantly better flame retardancy than amultilayer article including the latter films.

In some embodiments, the film 12 can have a maximum heat-release timemeasured in the cone calorimetry test at least about at least about 70seconds (e.g., at least about 75 seconds, at least about 80 seconds, atleast about 85 seconds, and at least about 90 seconds) and/or at mostabout 150 seconds (e.g., at most about 140 seconds, at most about 130seconds, at least about 120 seconds, or at least about 110 seconds).

In some embodiments, the film 12 can have a maximum heat-release ratemeasured in the cone calorimetry test lower than that of a film withoutany additive (e.g., by at least about 30%) or a film containing thenanoclay or the pore-forming filler alone (e.g., by at least about 10%,at least about 20%, or at least about 25%). As used herein, the term“maximum heat release rate” refers to the maximum heat released by asample per unit area per unit time. In general, the lower the maximumheat release rate, the better the flame retardancy. In some embodiments,the film 12 can have a maximum heat release rate measured in the conecalorimetry test at most about 450 kW/m² (e.g., at most about 400 kW/m²,at most about 350 kW/m², or at most about 300 kW/m²) and/or at leastabout at most about 100 kW/m² (e.g., at most about 150 kW/m² or at mostabout 200 kW/m²).

The pore-forming filler in the film 12 can generate pores uponstretching (e.g., by using a ring-rolling process during the manufactureof the multilayer article 10) to impart breathability to the film 12(i.e., to allow passage of vapor through the film 12).

The pore-forming filler can have a low affinity for and a lowerelasticity than the polyolefin component or the optional elastomercomponent. The pore-forming filler can be a rigid material. It can havea non-smooth surface, or have a surface treated to become eitherhydrophobic or hydrophilic.

In some embodiments, the pore-forming filler is in the form ofparticles. In such embodiments, the average value of the maximum lineardimension (e.g., the diameter) of the filler particles can be at leastabout 0.5 micron (at least about 1 micron or at least about 2 microns)and/or at most about 7 microns (e.g., at most about 5 microns or at mostabout 3.5 microns). Without wishing to be bound by theory, it isbelieved that a filler with a relatively small average value of themaximum linear dimension (e.g., from about 0.75 to 2 microns) canprovide a better balance of compoundability and breathability than afiller with a relatively large average particle size.

The pore-forming filler in the film 12 can be any suitable inorganic ororganic material, or combinations thereof. Examples of the inorganicfillers include calcium carbonate, talc, clay, kaolin, silicadiatomaceous earth, magnesium carbonate, barium carbonate, magnesiumsulfate, barium sulfate, calcium sulfate, aluminum hydroxide, zincoxide, magnesium oxide, calcium oxide, magnesium oxide, titanium oxide,alumina, mica, glass powder, glass beads (hollow or non-hollow), glassfibers, zeolite, silica clay, and combinations thereof. In someembodiments, the pore forming filler in the film 12 includes calciumcarbonate. In some embodiments, the inorganic pore-forming filler can besurface treated to be hydrophobic so that the filler can repel water toreduce agglomeration of the filler. In addition, the pore-forming fillercan include a coating on the surface to improve binding of the filler tothe polyolefin in the film 12 while allowing the filler to be pulledaway from the polyolefin when the film 12 is stretched or oriented(e.g., during a ring-rolling process). Exemplary coating materialsinclude stearates, such as calcium stearate. Examples of organic fillersthat can be used in film 12 include wood powder, pulp powder, and othercellulose-type powders. Polymer powders such as TEFLON powder and KEVLARpowder may also be included as an organic pore-forming filler. Thepore-forming fillers described above are either available fromcommercial sources or can be readily prepared by methods known in theart.

The film 12 can include a relatively high level of the pore-formingfiller as long as the level of the filler does not affect the formationof the film 12. For example, the film 12 can include from at least about30% (e.g., at least about 35%, at least about 40%, or at least about45%) to at most about 70% (e.g., at most about 65%, at most about 60%,or at most about 55%) by weight of the pore-forming filler (e.g.,calcium carbonate). In some embodiments, the film 12 can include about50% by weight of the pore-forming filler. Without wishing to be bound bytheory, it is believed that, if the film 12 does not include asufficient amount (e.g., at least about 30% by weight) of thepore-forming filler, the film may not have an adequate moisture vaportransmission rate (MVTR) (e.g., at least about 35 g/m²/day when measuredat 23° C. and 50 RH %). Further, without wishing to be bound by theory,it is believed that, if the film 12 includes too much (e.g., more thanabout 70%) of the pore-forming filler, the film 12 may not be uniform ormay have a low tensile strength.

The polyolefin in the film 12 facilitates formation of the film. As usedhere, the term “polyolefin” refers to a homopolymer or a copolymer madefrom a linear or branched, cyclic or acyclic alkene. Examples ofpolyolefins that can be used in film 12 include polyethylene,polypropylene, polybutene, polypentene, and polymethylpentene.

Exemplary polyethylene include low-density polyethylene (e.g., having adensity from 0.910 g/cm² to 0.925 g/cm²), linear low-densitypolyethylene (e.g., having a density from 0.910 g/cm² to 0.935 g/cm²),and high-density polyethylene (e.g., having a density from 0.935 g/cm²to 0.970 g/cm²). High-density polyethylene can be produced bycopolymerizing ethylene with one or more C₄ to C₂₀ α-olefin. Examples ofsuitable α-olefins include 1-butene, 1-pentene, 4-methyl-1-pentene,1-hexene, 1-octene, 1-decene, and combinations thereof. The high-densitypolyethylene can include up to 20 mole percent of the above-mentionedα-olefin comonomers. In some embodiments, the polyethylene suitable foruse in the film 12 can have a melt index in the range of from about 0.1g/10 min to about 10 g/10 min (e.g., from about 0.5 g/10 min to 5 g/10min).

Polypropylene can be used in the film 12 by itself or in combinationwith one or more of the polyethylene polymers described above. In thelatter case, polypropylene can be either copolymerized or blended withone or more polyethylene polymers. Both polyethylene and polypropyleneare available from commercial sources or can be readily prepared bymethods known in the art.

In some embodiments, the film 12 can further include a functionalizedpolyolefin (e.g., functionalized polyethylene or polypropylene), such asa polyolefin graft copolymer. Examples of such polyolefin graftcopolymers include polypropylene-g-maleic anhydride and polymers formedby reacting PP-g-MAH with a polyetheramine. In some embodiments, such afunctionalized polyolefin can be used a compatibilizer to minimize thephase separation between the components in the film 12 and/or to improveadhesion between the film 12 and the nonwoven substrate 14. Thecompatibilizer can be at least about 0.1% (e.g., at least about 0.2%, atleast about 0.4%, at least about 0.5%, at least about 1%, or at leastabout 1.5%) and/or at most about 30% (e.g., at most about 25%, at mostabout 20%, at most about 15%, at most about 10%, at most about 5%, atmost about 4%, at most about 3%, or at most about 2%) of the totalweight of film 12.

Optionally, the film 12 can include an elastomer (e.g., a thermoplasticolefin elastomer) to improve the elasticity of the film. Examples ofsuitable elastomers include vulcanized natural rubber, ethylene alphaolefin rubber (EPM), ethylene alpha olefin diene monomer rubber (EPDM),styrene-isoprene-styrene (SIS) copolymers, styrene-butadiene-styrene(SBS) copolymers, styrene-ethylene-butylene-styrene (SEBS) copolymers,ethylene-propylene (EP) copolymers, ethylene-vinyl acetate (EVA)copolymers, ethylene-maleic anyhydride (EMA) copolymers,ethylene-acrylic acid (EEA) copolymers, and butyl rubber. A commercialexample of such an elastomer is VERSIFY (i.e., an ethylene-propylenecopolymer) available from Dow (Midland, Mich.). The film 12 can includefrom about 5% (e.g., at least about 6% or at least about 7%) to at mostabout 30% (e.g., at most about 25%, at most about 20%, or at most about15%) by weight of the elastomer. Without wishing to be bound by theory,it is believed that one advantage of using an elastomer in the film 12is that the multilayer article 10 containing such a film can have bothimproved tensile strength (e.g., by at least about 5% or at least about10%) and improved elongation (e.g., by at least about 20% or at leastabout 50%).

The nonwoven substrate 14 can be formed from any suitable fibrousmaterials. As used herein, the term “nonwoven substrate” refers to asubstrate containing one or more layers of fibers that are bondedtogether, but not in an identifiable manner as in a knitted or wovenmaterial.

The nonwoven substrate 14 can be formed from any suitable polymers.Exemplary polymers that can be used to form the nonwoven substrate 14include polyolefins and polyesters. Examples of suitable polyolefinsinclude polyethylene, polypropylene, and copolymers thereof, such asthose in the film 12 described above. Examples of suitable polyestersinclude polyethylene terephthalate (PET), polybutylene terephthalate(PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate(PEN), polyglycolide or polyglycolic acid (PGA), polylactide orpolylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate(PEA), polyhydroxyalkanoate (PHA), and a copolymer thereof.

The nonwoven substrate 14 can be formed from single component fibers,i.e., fibers containing a polymer having a single chemical structure(e.g., a polymer described in the preceding paragraph such as apolyethylene, a polypropylene, or a polyethylene terephthalate). In someembodiments, the nonwoven substrate 14 can include single componentfibers made from polymers having the same chemical structure butdifferent characteristics (e.g., molecular weights, molecular weightdistributions, density, or intrinsic viscosities). For example, thenonwoven substrate 14 can include a mixture of a low-densitypolyethylene and a high-density polyethylene. Such fibers are stillreferred to as single component fibers in this disclosure.

The nonwoven substrate 14 can also be formed from multicomponent fibers,i.e., fibers containing polymers with different chemical structures(such as two different polymers described above). For example, thenonwoven substrate 14 can be formed from a mixture of a polypropyleneand a polyethylene terephthalate. In some embodiments, a multicomponentfiber can have a sheath-core configuration (e.g., having a polyethyleneterephthalate as the core and a polypropylene as the sheath). In someembodiments, a multicomponent fiber can include two or more polymerdomains in a different configuration (e.g., a side-by-sideconfiguration, a pie configuration, or an “islands-in-the-sea”configuration).

In some embodiments, the surface of the nonwoven substrate 14 cancontain a polymer having a chemical structure similar to (e.g., the sametype as) or the same as the chemical structure of a polymer in thesurface of the film 12. As an example, a polyolefin (e.g., apolyethylene or propylene) is of the same type as and similar to anotherpolyolefin (e.g., a polyethylene or propylene). Without wishing to bebound by theory, it is believed that such a film and substrate can haveimproved adhesion between these two layers. For example, when thenonwoven substrate 14 is formed from single component fibers, the fiberscan be made from a polyolefin, which has a chemical structure similar toor the same as the polyolefin in the film 12. When the nonwovensubstrate 14 is formed from multicomponent fibers (e.g., having asheath-core configuration), the polymer in the fibers that contacts thefilm 12 (e.g., the polymer in the sheath) can have a chemical structuresimilar to or the same as the chemical structure of one of the polymersin the film 12. Both examples described above can result in a multilayerarticle with improved adhesion between the film and the nonwovensubstrate.

The nonwoven substrate 14 can be made by methods well known in the art,such as a spunlacing, spunbonding, meltblowing, carding, air-throughbonding, or calendar bonding process.

In some embodiments, the nonwoven substrate 14 can be a spunbondednonwoven substrate. In such embodiments, the nonwoven substrate 14 caninclude a plurality of continuous fibers, at least some (e.g., all) ofwhich are bonded (e.g., area bonded or point bonded) with each otherthrough a plurality of intermittent bonds. The term “continuous fiber”mentioned herein refers to a fiber formed in a continuous process and isnot shortened before it is incorporated into a nonwoven substratecontaining the continuous fiber.

As an example, the nonwoven substrate 14 containing single componentfibers can be made by using a spunbonding process as follows.

After the polymer for making single component fibers is melted, themolten polymer can be extruded from an extruding device. The moltenpolymer can then be directed into a spinneret with composite spinningorifices and spun through this spinneret to form continuous fibers. Thefibers can subsequently be quenched (e.g., by cool air), attenuatedmechanically or pneumatically (e.g., by a high velocity fluid), andcollected in a random arrangement on a surface of a collector (e.g., amoving substrate such as a moving wire or belt) to form a nonwoven web.In some embodiments, a plurality of spinnerets with different quenchingand attenuating capability can be used to place one or more (e.g., two,three, four, or five) layers of fibers on a collector to form asubstrate containing one or more layers of spunbonded fibers (e.g., anS, SS, or SSS type of substrate). In some embodiments, one or morelayers of meltblown fibers can be inserted between the layers of theabove-described spunbonded fibers to form a substrate containing bothspunbonded and meltblown fibers (e.g., an SMS, SMMS, or SSMMS type ofsubstrate).

A plurality of intermittent bonds can subsequently be formed between atleast some of the fibers (e.g., all of the fibers) randomly disposed onthe collector to form a unitary, coherent, nonwoven substrate.Intermittent bonds can be formed by a suitable method such as mechanicalneedling, thermal bonding, ultrasonic bonding, or chemical bonding.Bonds can be covalent bonds (e.g., formed by chemical bonding) orphysical attachments (e.g., formed by thermal bonding). In someembodiments, intermittent bonds are formed by thermal bonding. Forexample, bonds can be formed by known thermal bonding techniques, suchas point bonding (e.g., using calender rolls with a point bondingpattern) or area bonding (e.g., using smooth calender rolls without anypattern). Bonds can cover between about 6 and about 40 percent (e.g.,between about 8 and about 30 percent or between about 22 and about 28percent) of the total area of the nonwoven substrate 14. Without wishingto be bound by theory, it is believed that forming bonds in the nonwovensubstrate 14 within these percentage ranges allows elongation throughoutthe entire area of the nonwoven substrate 14 upon stretching whilemaintaining the strength and integrity of the substrate.

Optionally, the fibers in the nonwoven substrate 14 can be treated witha surface-modifying composition after intermittent bonds are formed.Methods of applying a surface-modifying composition to the fibers havebeen described, for example, in U.S. Provisional Application No.61/294,328.

The nonwoven substrate thus formed can then be used to form multilayerarticle 10 described above. A nonwoven substrate containingmulticomponent fibers can be made in a manner similar to that describedabove. Other examples of methods of making a nonwoven substratecontaining multicomponent fibers have been described in, for example,U.S. Provisional Application No. 61/294,328.

The multilayer article 10 can be made by the methods known in the art orthe methods described herein. For example, the multilayer article 10 canbe made by first applying the film 12 (e.g., a film containing apolyolefin, a nanoclay, and a pore-forming filler) onto the nonwovensubstrate 14 to form a laminate. The film 12 can be applied onto thenonwoven substrate 14 by extruding (e.g., cast extrusion) a suitablecomposition (e.g., a composition containing a polyolefin, a nanoclay,and a pore forming filler) at an elevated temperature to form a filmonto the nonwoven substrate 14. In some embodiments, the just-mentionedcomposition can be extruded (e.g., by tubular extrusion or castextrusion) to form a web, which can be cooled (e.g., by passing througha pair of rollers) to form a precursor film. A laminate can then beformed by attaching the precursor film to the nonwoven substrate 14 byusing, for example, an adhesive (e.g., a spray adhesive, a hot-meltadhesive, or a latex-based adhesive), thermal bonding, ultrasonicbonding, or needle punching.

In some embodiments, the multilayer article 10 can include multiple(e.g., two, three, four, or five) films supported by the nonwovensubstrate 14, at least one of the films is the film 12 described above.Each of the films other than the film 12 can include one or morepolymers and one or more pore-forming fillers described above withrespect to the film 12. Optionally, one or more of the films other thanthe film 12 can include a nanoclay described above with respect to thefilm 12. In some embodiments, the nonwoven substrate 14 can be disposedbetween two of the multiple films. In some embodiments, all of the filmscan be disposed on one side of the nonwoven substrate 14.

FIG. 2 is a scheme illustrating an exemplary process for making alaminate described. As shown in FIG. 2, a suitable composition (e.g., acomposition containing a polyolefin, a nanoclay, and a pore-formingfiller) can be fed into an inlet 26 of an extruder hopper 24. Thecomposition can then be melted and mixed in a screw extruder 20. Themolten mixture can be discharged from extruder 20 under pressure througha heated line 28 to a flat film die 38. Extrusion melt 40 dischargingfrom the flat film die 38 can be coated on the nonwoven substrate 14from a roll 30. The coated substrate can then enter a nip formed betweenrolls 34 and 36, which can be maintained at a suitable temperature(e.g., between about 10-120° C.). Passing the coated substrate throughthe nip formed between the cooled rolls 34 and 36 can quench theextrusion melt 40 while at the same time compressing the extrusion melt40 so that it contacts the nonwoven substrate 14. In some embodiments,the roll 34 can be a smooth rubber roller with a low-stick surfacecoating while the roll 36 can be a metal roll. A textured embossing rollcan be used to replace the metal roll 36 if a multilayer article with atextured film layer is desired. When the extrusion melt 40 is cooled, itforms the film 12 laminated onto the nonwoven substrate 14. The laminatethus formed can then be collected on a collection roll 44. In someembodiments, the surface of the nonwoven substrate 14 can be corona orplasma treated before it is coated with the extrusion melt 40 to improvethe adhesion between the nonwoven substrate 14 and the film 12.

The laminate formed above can then be stretched (e.g., incrementallystretched or locally stretched) to form the vapor-permeable,substantially water-impermeable multilayer article 10. Without wishingto be bound by theory, it is believed that stretching the laminategenerates pores around the pore-forming filler in the film 12 that allowwater vapor to pass through. The laminate can be stretched (e.g.,incrementally stretched) in the machine direction (MD) or thecross-machine direction (CD) or both (biaxially) either simultaneouslyor sequentially. As used herein, “machine direction” refers to thedirection of movement of a nonwoven material during its production orprocessing. For example, the length of a nonwoven material can be thedimension in the machine direction. As used herein, “cross-machinedirection” refers to the direction that is essentially perpendicular tothe machine direction defined above. For example, the width of anonwoven material can be the dimension in the cross-machine direction.Examples of incremental stretching methods have been described in, e.g.,U.S. Pat. Nos. 4,116,892 and 6,013,151.

Exemplary stretching methods include ring rolling (in the machinedirection and/or the cross-machine direction), tentering, embossing,creping, and button-breaking. These methods are known in the art, suchas those described in U.S. Pat. No. 6,258,308 and U.S. ProvisionalApplication No. 61/294,328.

In some embodiments, the laminate described above can be stretched(e.g., incrementally stretched) at an elevated temperature as long asthe polymers in the laminate maintain a sufficient mechanical strengthat that temperature. The elevated temperature can be at least about 30°C. (e.g., at least about 40° C., at least about 50° C., or at leastabout 60° C.) and/or at most about 100° C. (e.g., at least about 90° C.,at least about 80° C., or at least about 70° C.). Without wishing to bebound by theory, it is believed that stretching the laminate describedabove at an elevated temperature can soften the polymers in the film 12and the nonwoven substrate 14, and therefore allow these polymers to bestretched easily. In addition, without wishing to be bound by theory, itis believed that stretching the laminate described above at an elevatedtemperature can increase the MVTR by increasing the number of the pores,rather than the size of the pores (which can reduce the hydrostatic head(i.e., resistance of water) of the multilayer article). As a result, itis believed that stretching the laminate described above at an elevatedtemperature can unexpectedly improve the MVTR of the resultantmultilayer article while still maintaining an appropriate hydrostatichead of the multilayer article.

FIG. 3 illustrates an exemplary ring-rolling apparatus 320 used toincrementally stretch the laminate described above in the cross-machinedirection. The apparatus 320 includes a pair of grooved rolls 322, eachincluding a plurality of grooves 324. The grooves 324 stretch thelaminate described above to form the multilayer article 10. In someembodiments, one or both of the rolls 322 can be heated to an elevatedtemperature (e.g., between about 30° C. and about 100° C.) by passing ahot liquid through the roll 322. The laminate described above can alsobe incrementally stretched in the machine direction in a similar manner.It is contemplated that the laminate can also be incrementally stretchedusing variations of the ring-rolling apparatus 320 and/or one or moreother stretching apparatus known in the art.

In some embodiments, the laminate described above can be embossed priorto or after being stretched (e.g., by using a calendering process). Forexample, the laminate can be embossed by passing through a pair ofcalender rolls in which one roll has an embossed surface and the otherroll has a smooth surface. Without wishing to be bound by theory, it isbelieved that an embossed multilayer article can have a large surfacearea, which can facilitate vapor transmission through the multilayerarticle. In some embodiments, at least one (e.g., both) of the calendarrolls is heated, e.g., by circulating a hot oil through the roll.

In some embodiments, the multilayer article 10 can have a suitable MVTRbased on its intended uses. As used herein, the MVTR values are measuredaccording to ASTM E96-A. For example, the multilayer article 10 can havea MVTR of at least about 35 g/m²/day (e.g., at least about 50 g/m²/day,at least about 75 g/m²/day, or at least about 100 g/m²/day) and/or atmost about 140 g/m²/day (e.g., at most about 130 g/m²/day, at most about120 g/m²/day, or at most about 110 g/m²/day) when measured at 23° C. and50 RH %. For instance, the multilayer article 10 can have a MVTR ofbetween 70 g/m²/day and 140 g/m²/day.

In some embodiments, the multilayer article 10 can have a sufficienttensile strength in the machine direction and/or the cross-machinedirection. The tensile strength is determined by measuring the tensileforce required to rupture a sample of a sheet material. The tensilestrength mentioned herein is measured according to ASTM D5034 and isreported in pounds. In some embodiments, the multilayer article 10 canhave a tensile strength of at least about 40 pounds (e.g., at leastabout 50 pounds, at least about 60 pounds, at least about 70 pounds, orat least about 80 pounds) and/or at most about 160 pounds (e.g., at mostabout 150 pounds, at most about 140 pounds, at most about 130 pounds, orat most about 120 pounds) in the machine direction. In some embodiments,the multilayer article 10 can have a tensile strength of at least about35 pounds (e.g., at least about 40 pounds, at least about 50 pounds, atleast about 60 pounds, or at least about 70 pounds) and/or at most about140 pounds (e.g., at most about 130 pounds, at most about 120 pounds, atmost about 110 pounds, or at most about 100 pounds) in the cross-machinedirection.

As a specific example, when the multilayer article 10 has a unit weightof 1.25 ounce per square yard, it can have a tensile strength of atleast about 40 pounds (e.g., at least about 45 pounds, at least about 50pounds, at least about 55 pounds, or at least about 60 pounds) and/or atmost about 100 pounds (e.g., at most about 95 pounds, at most about 90pounds, at most about 85 pounds, or at most about 80 pounds) in themachine direction, and at least about 35 pounds (e.g., at least about 40pounds, at least about 45 pounds, at least about 50 pounds, or at leastabout 55 pounds) and/or at most about 95 pounds (e.g., at most about 90pounds, at most about 85 pounds, at most about 80 pounds, or at mostabout 75 pounds) in the cross-machine direction.

In some embodiments, the multilayer article 10 can have a sufficientelongation in the machine direction and/or the cross-machine direction.Elongation is a measure of the amount that a sample of a sheet materialwill stretch under tension before the sheet breaks. The term“elongation” used herein refers to the difference between the lengthjust prior to breaking and the original sample length, and is expressedas a percentage of the original sample length. The elongation valuesmentioned herein are measured according to ASTM D5034. For example, themultilayer article 10 can have an elongation of at least about 5% (e.g.,at least about 10%, at least about 20%, at least about 30%, at leastabout 35%, or at least about 40%) and/or at most about 100% (e.g., atmost 90%, at most about 80%, or at most about 70%) in the machinedirection. As another example, the multilayer article 10 can have anelongation of at least about 5% (e.g., at least about 10%, at leastabout 20%, at least about 30%, at least about 35%, or at least about40%) and/or at most about 100% (e.g., at most about 90%, at most about80%, or at most about 70%) in the cross-machine direction.

In some embodiments, the multilayer article 10 can have a sufficienthydrostatic head value so as to maintain sufficient waterimpermeability. As used herein, the term “hydrostatic head” refers tothe pressure of a column of water as measured by its height that isrequired to penetrate a given material and is determined according toAATCC 127. For example, the multilayer article 10 can have a hydrostatichead of at least about 55 cm (e.g., at least about 60 cm, at least about70 cm, at least about 80 cm, at least about 90 cm, or at least about 100cm) and/or at most about 900 cm (e.g., at most about 800 cm, at mostabout 600 cm, at most about 400 cm, or at most about 200 cm).

The multilayer article 10 can be used in a consumer product with orwithout further modifications. Examples of such consumer productsinclude construction materials, such as a housewrap or a roofwrap. Otherexamples include diapers, adult incontinence devices, feminine hygieneproducts, medical and surgical gowns, medical drapes, and industrialapparels.

While certain embodiments have been disclosed, other embodiments arealso possible.

In some embodiments, an effective amount of various additives can beincorporated in either the film 12 or the nonwoven substrate 14.Suitable additives include pigments, antistatic agents, antioxidants,ultraviolet light stabilizers, antiblocking agents, lubricants,processing aids, waxes, coupling agents for fillers, softening agents,thermal stabilizers, tackifiers, polymeric modifiers, hydrophobiccompounds, hydrophilic compounds, anticorrosive agents, and mixturesthereof. In certain embodiments, additives such as polysiloxane fluidsand fatty acid amides can be included to improve processabilitycharacteristics.

Pigments of various colors can be added to provide the resultantmultilayer article 10 that is substantially opaque and exhibits uniformcolor. For example, the multilayer article 10 can have a sufficientamount of pigments to produce an opacity of at least about 85% (e.g., atleast about 90%, at least about 95%, at least about 98%, or at leastabout 99%). Suitable pigments include, but are not limited to, antimonytrioxide, azurite, barium borate, barium sulfate, cadmium pigments(e.g., cadmium sulfide), calcium chromate, calcium carbonate, carbonblack, chromium(III) oxide, cobalt pigments (e.g., cobalt(II)aluminate), lead tetroxide, lead(II) chromate, lithopone, orpiment,titanium dioxide, zinc oxide and zinc phosphate. Preferably, the pigmentis titanium dioxide, carbon black, or calcium carbonate. The pigment canbe about 1 percent to about 20 percent (e.g., about 3 percent to about10 percent) of the total weight of the nonwoven substrate 14 or the film12. Alternatively, the pigment can be omitted to provide a substantiallytransparent multilayer article.

In some embodiments, certain additives can be used to facilitatemanufacture of the multilayer article 10. For example, antistatic agentscan be incorporated into the nonwoven substrate 14 or the film 12 tofacilitate processing of these materials. In addition, certain additivescan be incorporated in the multilayer article 10 for specific endapplications. For example, anticorrosive additives can be added if themultilayer article 10 is to be used to package items that are subject tooxidation or corrosion. As another example, metal powders can be addedto provide static or electrical discharge for sensitive electroniccomponents such as printed circuit boards.

The nonwoven substrate 14 or the film 12 can also include a filler. Theterm “filler” can include non-reinforcing fillers, reinforcing fillers,organic fillers, and inorganic fillers. For example, the filler can bean inorganic filler such as talc, silica, clays, solid flame retardants,Kaolin, diatomaceous earth, magnesium carbonate, barium carbonate,magnesium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide,magnesium hydroxide, calcium oxide, magnesium oxide, alumina, mica,glass powder, ferrous hydroxide, zeolite, barium sulfate, or othermineral fillers or mixtures thereof. Other fillers can include acetylsalicylic acid, ion exchange resins, wood pulp, pulp powder, borox,alkaline earth metals, or mixtures thereof. The filler can be added inan amount of up to about 60 weight percent (e.g., from about 2 weightpercent to about 50 weight percent) of the nonwoven substrate 14 or thefilm 12.

In some embodiments, the surface of the nonwoven substrate 14 or thefilm 12 can be at least partially treated to promote adhesion. Forexample, the surface of the nonwoven substrate 14 or the film 12 can becorona charged or flame treated to partially oxidize the surface andenhance surface adhesion. Without wishing to be bound by theory, it isbelieved that the multilayer article 10 having enhanced surface adhesioncan enable printing on its surface using conventional inks. Ink-jetreceptive coating can also be added to the surface of the multilayerarticle 10 to allow printing by home or commercial ink jet printersusing water based or solvent based inks.

The following examples are illustrative and not intended to be limiting.

Example 1

The following multilayer article samples were used in a cone calorimetrytest according to ASTM E1354: (1) TYPAR (i.e., a polypropylenespunbonded nonwoven substrate available from Fiberweb, Inc.) coated witha film containing polypropylene alone, (2) TYPAR coated with a filmcontaining polypropylene and a NANOMER I44P nanoclay available fromNanocor, Inc., (3) TYPAR coated with a film containing polypropylene andcalcium carbonate, and (4) TYPAR coated with a film containingpolypropylene, the above-mentioned NANOMER I44P nanoclay, and calciumcarbonate. The NANOMER I44P nanoclay was 2% of the total weight of thefilms in samples (2) and (4), and the calcium carbonate was 50% of thetotal weight of the films in samples (3) and (4). For each sample, thefilm was coated onto TYPAR by extrusion coating.

The results of the cone calorimetry test are illustrated in FIG. 4. Asshown in FIG. 4, when sample (2) (which includes a polypropylene filmcontaining a nanoclay) and sample (3) (which includes a polypropylenefilm containing calcium carbonate, i.e., a pore-forming filler)exhibited a maximum heat release time about 5-15% shorter than that ofsample (1) (which includes a polypropylene film without any additive).Unexpectedly, sample (4) (which includes a polypropylene film containingboth the nanoclay and the calcium carbonate) exhibited a maximum heatrelease time at least about 5% longer than that of sample (1) andtherefore also longer than those of samples (2) and (3). In general, amaterial having a longer maximum release time possesses better heatretardancy.

Example 2

The tensile strength and elongation of the following multilayer articlesamples were measured according to ASTM D5034: (1) TYPAR (i.e., apolypropylene spunbonded nonwoven substrate having a unit weight of 1.9ounces per square yard available from Fiberweb, Inc) coated with a filmcontaining polypropylene and calcium carbonate and (2) TYPAR coated witha film containing polypropylene, calcium carbonate, and VERSIFY (apropylene-ethylene elastomer available from The Dow Chemical Company).For each sample, the film was coated onto TYPAR by extrusion coating.

The results of the above tests are summarized in Table 1 below.

TABLE 1 Tensile Tensile Elongation Elongation MD CD MD CD SampleComponents (Lbs) (Lbs) (%) (%) (1) TYPAR coated 90.7 98.1 25.7 21.6 with70 wt % PP/30 wt % CaCO₃ (2) TYPAR coated 100.3 106.9 31.1 33.3 with 50wt % PP/20 wt % VERSIFY/ 30 wt % CaCO₃

As shown in Table 1, sample (2) unexpectedly exhibited improved tensilestrength and elongation in both the machine and cross-machinedirections.

Other embodiments are in the claims.

What is claimed is:
 1. A method of making an article, comprising:forming a laminate comprising (i) a nonwoven substrate comprising aplurality of intermittent bonds defining a bonded area from about 6% toabout 40%, and (ii) a film supported by the nonwoven substrate, the filmcomprising a polyolefin, a nanoclay, and a pore-forming filler; andstretching the laminate to form pores in the film and to provide thearticle; wherein the article has a moisture vapor transmission rate ofat least about 35 g/m²/day to at most about 140 g/m²/day when measuredat 23° C. and 50 RH % and the article has an elongation of at leastabout 5% to about 100% as measured according to ASTM D5034.
 2. Themethod of claim 1, wherein forming the laminate comprises extruding thefilm onto the nonwoven substrate.
 3. The method of claim 1, wherein thestep of stretching the laminate is performed at an elevated temperaturethat is at least about 30° C.
 4. The method of claim 1, wherein thelaminate is stretched in the machine direction.
 5. The method of claim1, wherein the laminate is stretched in the cross-machine direction. 6.The method of claim 1, wherein the laminate is stretched by a methodselected from the group consisting of ring rolling, tentering,embossing, creping, and button-breaking.
 7. The method of claim 1,further comprising embossing the laminate before or after stretching thelaminate.
 8. The method of claim 1, further comprising bonding randomlydisposed polymeric fibers to produce the nonwoven substrate beforeforming the laminate.
 9. The method of claim 1, wherein the nanoclaycomprises particles having an average aspect ratio of from 200 to about500.
 10. The method of claim 1, wherein the nanoclay has an averagethickness of from about 0.5 nm to about 2 nm.
 11. The method of claim 1,wherein the film comprises from about 0.1% by weight to about 20% byweight of the nanoclay.
 12. The method of claim 1, wherein thepolyolefin comprises a polyethylene, a polypropylene, or a copolymerthereof.
 13. The method of claim 12, wherein the film further comprisesa functionalized polyolefin.
 14. The method of claim 1, wherein thepore-forming filler comprises from about 30% by weight to about 70% byweight of a plurality of calcium carbonate particles.
 15. The method ofclaim 1, wherein the film further comprises an elastomer.
 16. The methodof claim 15, wherein the elastomer is a thermoplastic olefin elastomer.17. The method of claim 15, wherein the film comprises from about 5% byweight to about 30% by weight of the elastomer.
 18. The method of claim1, wherein the nonwoven substrate comprises randomly disposed polymericfibers, at least some of the fibers being bonded to one another.